Heat exchanger

ABSTRACT

Heat exchanger comprising a bundle of a plurality of triple tubes each of which consists of heating fluid passing tube and a heat transfer tube with a closed end at the position near the heating fluid inlet end of the heating fluid passing tube, and an inner tube provided in the heat transfer tube with an open end near the closed end of the heating fluid passing tube.

[451 Sept. 9, 1975 United States Patent [191 Fuki et al.

References Cited UNITED STATES PATENTS HEAT EXCHANGER Inventors: Ichiro Fuki; Shosaku Shimizu, both of Tamano; Etsuji Yamamoto;

. r m m h 8 mm m .m w wu r 10. u a c mu h C 3344 r 9999 M 1111 l 2527 m a a 8725 7372 y r 5725 m 4 37 n 222 P Assistant Examiner'lheophil W. Streule, Jr.

Attorney, Agent, or F irml-lowson and Howson [22] Filed: Mar. 1, 1974 [21] Appl. No.: 447,206

[ ABSTRACT Heat exchanger comprising a bundle of a plurality of Foreign Application Prioriiy Data triple tubes each of which consists of heating fluid Mar. 6, 1973 Passing tube and a heat transfer tube With a Closed end at the position near the heating fluid inlet end of the heating fluid passing tube, and an inner tube provided in the heat transfer tube with an open end near the closed end of the heating fluid passing tube.

2 Claims, 4 Drawing Figures HEAT EXCHANGER v This invention relates to a heat exchanger for use in boilers and the like. In the conventional design of the heat exchanger, the heat transfer tubes are secured at one end or both ends to headers. When the heat exchanger comprising heat transfer tubes secured at both ends is operated under high temperature (for instance 350 to 600C), heat transfer tubes of the heat exchanger are subjected to considerable thermal stress, even if the tubes are spirally wound to absorb deformations due to thermal expansion.

Therefore, it is an object of this invention to provide a heat exchanger which can remove the aforementioned disadvantage. In accordance with this invention, the heat exchanger comprises a bundle of a number of triple tubes, each of which consists of a heating fluid passing tube with both ends flared to form tube plates and a double tube inserted therein which comprises an outer heat transfer tube and an inner tube. Further, in accordance with this invention thermal stress is not caused in the heat transfer tubes because the tubes are secured only at one end. On the other hand, in order to remove the fouling deposited on the heat transfer tubes, it is possible to superheat the tubes by operating the heat exchanger without cooling water, so that the fouling is burnt to be exhausted without removing the heat transfer tubes from the drum.

This invention will now be explained with reference to the accompanying drawings, in which:

FIG. 1 is a vertical sectional view of a heat exchanger in accordance with this invention;

FIG. 2 is an illustration as viewed from arrow AA in FIG. 1;

F IG. 3 is a sectional view taken along lines B-C-D in FIG. 2; and

FIG. 4 is a vertical section of another embodiment of this invention.

Referring to FIG. 1, a cylindrical drum generally designated by numeral 1 is provided inside with a number of gas passage tubes 2 and double tubes inserted into said gas passage tubes respectively, each of said double tubes comprising an inner tube 3 and an outer heat transfer tube 4. The gas passage tubes 2 are made of heat resisting steel and disposed in triangular arrangement. Both ends of each gas passages tube are flared in the hexagonal shape as illustrated in FIG. 2. The upper end of each gas passage tube is welded to the upper ends of adjacent gas passage tubes to form a tube plate, while the lower ends of the gas passage tubes are free without welding to each other, but their flared ends act as a tube plate. The upper end of the so formed tube bundle is welded to a ring 5 at the peripheral edge, which in turn is welded to a drum mantle 6 to support the gas passage tubes. The periphery of the lower end of the tube bundle is sealed by the gland 10. Inside of the drum mantle 6, an inner lining of insulating material 11 is provided. The lower end of the drum mantle 6 is connected to a gas inlet cover 8 lined with an inner lining 7 ofinsulating material by a pair of flanges 9. The upper end of the drum mantle 6 is connected to a gas outlet chamber 18, having an outlet 17, by a pair of flanges 19. The separator drum is provided with a water supply box 21 and connected to the upper end of the drum 1. The upper end of each inner tube 3 is secured to the bottom of the water supply box 21 and communicated therein. The upper end of each heat transfer tube 4 is secured to the bottom of the separator drum 20 and opens into the drum. The lower end of each heat transfer tube 4 terminates near the lower end of the gas passage tube 2 and is closed with the spherical shape as shown in FIG. 3. The lower end of the inner tube 3 terminates near the lower end of the heat transfer tube 4 and is opened.

In operation, gas such as cracked gas is introduced into the drum 1 through the inlet 31 and ascends the spaces between the tubes 2 and 4 and exhausts from the outlet 17 provided on the side of the gas outlet chamber 18. On the other hand, liquid to be heated is introduced into the box 21 in the separator drum 20 through the supply pipe 22 and descends in tubes 3 and ascends in the space between the tubes 3 and 4 after turning at the bottom of the tube 4 and returns to the box 21. Thus the liquid is recycled in the device. Steam generated in the tubes 4 ascends in the tubes and the drum 20 and exhausts from the outlet 23.

The heat exchanger shown in FIG. 4 may treat two kinds of heating fluid which are different in properties such as boiling point from each other. The device has two heat exchange parts 24 and 25 and an intermediate outlet chamber 26 provided with an outlet 27. The gas outlet 28 is provided with a branch nozzle 29 and a shut off valve 30. Corresponding parts to those of the device shown in FIG. 1 and designated by the same numerical references as in FIG. 1.

In the case that the whole device is usedfor cooling the gas to a considerably lower temperature, the outlet 27 is closed. In the case that if the gas to be treated is over cooled by the whole device, there will be generated a condensation of material contained in the gas, the valve 30 is closed and a pressure gas such as steam is introduced from the branch nozzle 29 in order to prevent the gas to be treated from ascending throughthe heat exchange part 24 so that the gas is exhausted from the outlet 27. Thus the heat transferring area is decreased and the temperature of exhaust gas is increased, whereby the gas of high boiling point material may be treated without deposition of the condensate on the heat transfer surface.

It will be understood that the present invention may be embodied in the type of heat exchanger in which the tube bundle is provided in the horizontal position. Further, upper ends of tubes 3 and 4 may be connected to headers respectively, which headers are connected to a separator drum.

From the foregoing, it will be understood that this invention provides a heat exchanger in which heat trans fer tubes are not subjected to thermal stress, because thermal expansion of each tube is permitted at the free end thereof.

What is claimed is:

1. A heat exchanger, comprising:

a drum having a heating fluid inlet and a heating fluid outlet;

a plurality of heating fluid passing tubes disposed parallel to each other in said drum between said heating fluid inlet and said heating fluid outlet, each of said heating fluid passing tubes being open at both ends;

at least one heat transfer tube in each of said heating fluid passing tubes, that end of each of said heat transfer tubes positioned nearer said heating fluid inlet being closed;

at least one inner tube disposed in each of said heat transfer tubes and open at the end thereof nearer tubes nearer said heating fluid inlet free to expand and contract with respect to said drum in response to temperature changes.

2. The heat exchanger of claim 1, in which the fluid inlet end of each of said heating fluid passing tubes is flared into a hexagonal cross section, each of said flared ends being positioned adjacent but spaced from others of said flared ends. 

1. A heat exchanger, comprising: a drum having a heating fluid inlet and a heating fluid outlet; a plurality of heating fluid passing tubes disposed parallel to each other in said drum between said heating fluid inlet and said heating fluid outlet, each of said heating fluid passing tubes being open at both ends; at least one heat transfer tube in each of said heating fluid passing tubes, that end of each of said heat transfer tubes positioned nearer said heating fluid inlet being closed; at least one inner tube disposed in each of said heat transfer tubes and open at the end thereof nearer said closed end of said heat transfer tube in which it is disposed; means for flowing a liquid through said inner tubes aNd heat transfer tubes; and tube mounting means for mounting said tubes to said drum; said mounting means fixedly securing said heat transfer tubes, said heating fluid passing tubes and said inner tubes to said drum at the ends thereof which are more remote from said heating fluid inlet, while leaving the ends of each of said tubes nearer said heating fluid inlet free to expand and contract with respect to said drum in response to temperature changes.
 2. The heat exchanger of claim 1, in which the fluid inlet end of each of said heating fluid passing tubes is flared into a hexagonal cross section, each of said flared ends being positioned adjacent but spaced from others of said flared ends. 